An agricultural vehicle known as a “combine” is historically termed such because it combines multiple harvesting functions with a single harvesting unit, such as picking, threshing, separating, and cleaning. A combine generally includes a header, a feeder housing, a threshing rotor, and various other systems for the separation, cleaning, and temporary storage of the crop material. The header removes the crop material from a field and transports the crop material to the feeder housing.
A typical header for an agricultural vehicle includes one or more cutters, e.g., cutter bars with reciprocating knives, which cut the crop material that is harvested from the field. Generally, the cutter bars are driven in a linearly reciprocal manner by a knife drive, such as a “wobble box” or epicyclic gear drive. The knife drive is usually powered by a mechanical drivetrain that extends from the combine. Thereby, the knife drive converts rotary motion from the mechanical drivetrain into a linear motion that drives the cutter bar. As is common with some larger headers, the cutter bar may be split into two separate halves, which are each separately driven. This particular type of cutter bar may be referred to as a dual reciprocating-knife cutter bar.
Reciprocating-knife cutter bars may negatively impact the function and life of the header due to the generation of vibration the cutter bar as the knife drive(s) cyclically accelerate the mass of each cutter bar section. For example, the header may experience unwanted forces which reduce its operating life, and the cutter bar may strip the crop material instead of cleanly severing the crop material from the ground. To reduce this vibration, a dual reciprocating cutter bar is often “timed” to have the cutter bar sections reciprocate in opposing directions, so that the forces acting to move the two knives cancel each other. However, issues may still persist as the cutter bar halves may subsequently become unsynchronized or untimed due to slight differences in speed between the two cutter bar halves.
Some dual reciprocating cutter bars include additional components to ensure proper synchronization of the cutter bar halves. U.S. Pat. No. 8,973,345 discloses a centrally located synchronization transmission that is coupled to each cutter bar section, and which forces each section to move with a 180-degree phase shift relative to one another. U.S. Pat. No. 7,658,059 discloses a synchronous drive system that includes a controller, a pair of sensors, and a pair of hydraulic motors that are coupled to a hydraulic valve and which respectively drive the cutter bar sections. The controller monitors the position of each cutter bar section via the sensors, and the controller manipulates the valve to synchronize the motors by bleeding off a portion of the hydraulic fluid flow to slow down the master motor so that it matches the speed of the slave motor. Thus, the cutter bar halves will reach the end of their strokes at the same time. However, such prior art solutions may be complex, costly to maintain, and may increase manufacturing costs.
What is needed in the art is a cost-effective and reliable synchronization system for synchronizing a dual reciprocating-knife cutter bar.